The interferometer is an instrument to make intensity change by the phase angle difference between two interfering coherent light beams. Two famous types of the interferometer are Michelson interferometer and Mach-Zehnder interferometer. Importantly, phase angle determination from the intensity change in the interferometer is an area that needs improvement. The bright spot and dark spot in the interferometer indicate in-phase and out-of-phase interference of two coherent beams. By counting the intensity maxima and minima during a movement, one can determine the displacement of a reflective object and measure the distance very accurately. Currently, several interferometric displacement sensors are commercialized in the market However, the conventional interferometric displacement sensors are designed for one or a few spot measurement only. Also, the conventional interferometric sensors are designed to measure the distance change only and are not designed to characterize an optical material inside a beam path. Accordingly, a need exists for expanding the measurement capability of an interferometer, which can improve its use for material characterization, among other activities.